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Blunted responses of doppler-derived aortic flow parameters during whole-body heavy isometric exercise in heart
I Auerbach1, A Tenenbaum, M Motro
1Cardiac Rehabilitation Institute, Sheba Medical Center, Tel-Hashomer, Israel. ila1@internet-zahav.net
Background:
Relatively light isometric exercise (handgrip) in heart transplant recipients induces attenuated increments in heart rate, blood pressure, and systemic vascular resistance, but hemodynamic response to whole-body, heavy isometric exercise is unknown. The aim of our study was to investigate the influences of whole-body, heavy, isometric exercise on Doppler-derived parameters in these patients.
Methods:
We investigated 18 patients, aged 54.0 +/- 2 years, 1.6 +/- 1.0 years after cardiac transplantation and 18 sedentary healthy volunteers, aged 51.8 +/- 4 years (p = not significant). Patients performed supine, isometric exercise by stretching a whole-body isometric device at 50% of maximal voluntary contraction for 3 minutes.
Results:
Resting heart rate, blood pressure, and rate-pressure product were higher in transplanted patients when compared with the healthy volunteers (p < 0.001 for all). However, during isometric exercise, these parameters increased to a lesser extent in the transplanted compared with the healthy subjects-heart rate, 12% vs 40% (p < 0.001); mean arterial pressure, 20% vs 27% (p < 0.05); and rate-pressure product, 39% vs 85% (p < 0.001). In the healthy volunteers, peak-flow velocity, mean acceleration, flow-velocity integral, and stroke volume decreased by 30% to 40% with isometric exercise (p < 0.001 for all), whereas systemic vascular resistance increased by 36% (p < 0.001) and cardiac output did not change. In the transplanted patients, all above parameters remained unchanged. Heavy, whole-body isometric exercise was well tolerated in heart transplant recipients in this study, without hemodynamic deterioration or other complications.
Conclusions:
With whole-body, heavy isometric exercise, Doppler-derived aortic flow parameters demonstrate blunted responses or remain unchanged among heart transplant recipients. The observed phenomenon may have implications for studies of exercise physiology in transplant recipients.
